Movie films with dual sound tracks are often used, for example, in a bilingual production or to provide stereophonic sound. Dual sound tracks have not normally been available except on 16 mm. or 35 mm. film. There are situations where the smaller size and weight of an 8 mm. projector and film make it preferable. As an illustration, in-flight movies shown on commercial airlines commonly use 8 mm. equipment. However, many flights on which movies are shown are international, and often carry passengers who do not speak the same language. The ability to utilize bilingual sound tracks would enable more viewers to enjoy the film.
A standard 8 mm. movie film does not have a provision for a second optical sound track. The Super-8 film format, however, has an image location which leaves a margin along one edge that is used for a primary optical sound track. There is also a margin, although narrower, between the sprocket holes and the other film edge.